By 1938, the Soviet Union had decided to conquer Finland. Intelligence compiled partly from Finnish communists filled a 200-page book detailing roads, bridges, and infrastructure, which was distributed to the invasion force. The Soviet 14th Army received orders to drive between Kuhmo and Salla, splitting the country along the Gulf of Bothnia. The 122nd Rifle Division, freshly arrived from Poland on 8 November 1939, drew the Salla assignment. Their timetable allowed two weeks to reach Rovaniemi — roughly the pace of a peacetime road march. The Soviets expected only light resistance. To support the advance, 100,000 prisoners had been forced to build a railroad from Kandalaksha toward the Finnish border, and new roads now connected the Murmansk Railway to forward staging areas. Everything pointed to a swift, overwhelming thrust. Everything except the terrain.

Southern Lapland is eighty percent forest and swamp. In early December 1939, the lakes and bogs had not yet frozen hard enough to bear vehicles, funneling all movement onto a single road from the Soviet border to Salla. West of the village the road network branched, but east of it there was only one way in and one way out. For a modern mechanized division, this was a chokepoint disguised as a highway. As winter deepened and temperatures plunged to minus forty degrees Celsius, frostbite became as dangerous as Finnish rifles. The cold cracked engine blocks, jammed weapons, and sapped the will of soldiers dressed for a short campaign. The Finns, by contrast, moved on skis through forest their opponents could not enter, appearing and vanishing like ghosts along the Soviet flanks.

Finland's defenders near Salla were almost absurdly outnumbered. The 17th Separate Battalion — known as the Salla Battalion — had been mobilized from a company of the Frontier Guard. Reinforcements trickled in after 5 December, but the total Finnish strength in the area never exceeded about 3,500 troops. The general staff knew this was insufficient, yet the critical fighting on the Karelian Isthmus demanded every available man. What the Finns lacked in numbers, they compensated for with terrain knowledge and tactical agility. By 17 December, seven Finnish battalions faced the Soviet 122nd and 88th Divisions west of Salla under the newly formed Lapland Group, commanded by Major General Kurt Martti Wallenius. On 18 December, a Finnish night attack at Pelkosenniemi panicked the northern Soviet column so badly that it fled ten miles back to Raatikka. Two days later, the southern thrust stalled outside Joutsijärvi. The road to Kemijärvi was shut.

Soviet forces had pushed the Finns back to the Kemijoki River, but they could advance no farther. Their supply lines now stretched 145 kilometers through hostile forest — a logistical nightmare in any season, a death sentence in the Arctic winter. Finnish ski troops began slicing into those supply columns, hitting convoys and vanishing into the trees before a response could be organized. The raids were so effective that a third of all Soviet troops in the sector were eventually diverted to guard their own supply roads rather than fight at the front. On 13 January 1940, the Soviet 9th Army ordered the 122nd Division to fall back to Märkäjärvi. What followed was two months of frozen stalemate — small skirmishes, artillery exchanges, and the grinding attrition of soldiers enduring conditions that tested the limits of human endurance on both sides.

In late February 1940, exhausted Finnish troops received unexpected relief: Swedish, Norwegian, and Danish volunteers of the Stridsgruppen SFK arrived to take their place in the line. These Scandinavian volunteers had crossed the border to help a neighbor under siege, and they would pay a steep price for it. On 13 March — the very last day of the Winter War — the Soviets launched a massive bombardment with artillery, aircraft, and infantry weapons, the opening salvo of a renewed offensive toward Rovaniemi. The volunteers suffered their worst single day: ten killed and thirty wounded. Then the ceasefire came. When the final toll was counted, Finnish casualties stood at 1,100, including 650 dead or missing. The Scandinavian volunteers lost 33 dead, 50 wounded, and 130 frostbitten. Soviet losses are estimated at 4,000. The two-week timetable had become three and a half months of futility. Finland was never cut in two.